Experimental research on heat transfer performance of CO2 low temperature heat pipe

With the development of applications in the sub-zero temperature region, the high performance heat transfer element, heat pipe is expected to play an important role in this field. However, suitable working fluid for low temperature heat pipe is limited, the two commonly used substances, Freon and ammonia are environmentally harmful. In contrast, carbon dioxide (CO2) is an environmentally friendly gas and can be a promising candidate working fluid for low temperature heat pipe because of its suitable thermal properties. At present, CO2 heat pipes are seldom investigated and used in the sub-zero temperature region. So, the heat transfer performance of CO2 heat pipe is experimentally investigated, and influences of heat loads, filling ratios, condenser conditions (temperature, length, and position) are investigated. The results show that the performance of CO2 heat pipe is satisfactory, its thermal resistance can be 0.2-0.4K/W and its equivalent thermal conductivity can be 3.7 x 10(4) W/(m.K). Besides, the performance of R134a heat pipe is investigated as a control group, it is found that its thermal resistance is 2-5 times that of CO2 heat pipe in sub-zero temperature region. The results illustrate that the CO2 heat pipe has a good application prospect in the field of low temperature range from -50 degrees C to 0 degrees C. (C) 2021 Elsevier Ltd. All rights reserved.

Automated summary

With the development of applications in the sub-zero temperature region, the potential use of carbon dioxide (CO2) as a working fluid for low temperature heat pipes is explored. Experimental results show promising performance of CO2 heat pipes, with thermal resistance ranging from 0.2-0.4K/W and equivalent thermal conductivity of 3.7 x 10(4) W/(m.K).